The excess pressure in water pipes can be used to spin miniature hydroelectric turbines, providing an underutilised source of clean energy. Some envision a distributed network of small turbines serving as a form of reliable storage to back up wind and solar power.
“I think it is a very under-tapped resource,” says at the Low Impact Hydropower Institute, an environmental non-profit based in Massachusetts. “The infrastructure is there; adding a turbine into the infrastructure makes a lot of sense.”
This type of “in-conduit” hydropower , according to a 2022 study by researchers at Oak Ridge National Laboratory in Tennessee. If such systems were installed at all potential sites in the country, the study estimated this could provide at least 1.41 gigawatts of additional capacity – equivalent to around 450 onshore wind turbines – without requiring any large new infrastructure to be built.
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“Billions of miles of pressurised pipelines exist in the world,” says at InPipe Energy, an Oregon-based company that has installed three such systems, including one that outside of Portland. The company’s to a pipe carrying drinking water to people in the East Bay Municipal Utilities District (EBMUD) in California started generating power in November.
The EBMUD system is expected to generate 130,000 kilowatt-hours of electricity per year, which will be used to power nearby water pumps. Any excess power will be sent to the grid, helping the utility move towards its target of carbon neutrality by 2030, says at EBMUD. The project is predicted to reduce the utility’s carbon dioxide emissions by about 6 tonnes each year.
Semler says a similar system will be installed in Aurora, Colorado, in April, and that InPipe is in discussions with the New York City government about ways to generate electricity from the nearly 4 billion litres of water that flow into the metropolis every day. Eventually, he envisions water utilities with networks of small systems working in concert as a form of hydropower storage backing up intermittent renewables.
“If there was no sun, or there was no wind, water utilities could put more water through the pipes to produce more energy,” he says.
InPipe’s system serves the same function as a regular pressure valve, which dissipates the excess water pressure generated by gravity and pumps. Instead of simply releasing this pressure, however, InPipe’s technology uses it to generate electricity. In parallel to an existing valve, the system diverts piped water through a bypass, where it spins a hydroelectric turbine before returning it to the pipe. “We don’t change the flow of the water, but we take out pressure,” says Semler.
This is different from the approach taken by Semler’s previous company, Lucid Energy, which aimed to generate power by placing turbines directly within existing pipes. The company – which has since shuttered – . But Semler says convincing water utilities to cut open their pipes and abandon existing pressure valves to generate electricity proved difficult.
Other hydropower companies, such as and , have developed similar in-conduit hydropower systems, and the idea has been around for at least two decades. But only a hundred or so have been installed, says at Rentricity, a New York City-based company that has installed more than 30 systems across the US.
However, Zammataro thinks such systems could soon be adopted more widely. He says the industry is at an “inflection point” thanks to a new emphasis on cutting emissions, support for upgrading infrastructure and growing track record of in-conduit systems. “We’re not going to break your pipes,” he says.
